Nylon Fiber Leukapheresis: Associated Complement Component Changes and Granulocytopenia

Abstract

The possible role of complement activation in the development of transient granulocytopenia during nylon fiber filtration leukapheresis (FL) was studied in five normal donors. No changes in hemolytic complement (CH50) titers were observed in the donors’ circulating plasma at any point in the procedure. However, comparison of pre- and postfilter blood samples drawn 1 min after donor blood passed the filters revealed decreases in several complement (C) components in postfilter plasma. Marked reductions in CH50, hemolytic C4 and C2, and properdin protein levels were observed, as well as moderate but significant reductions in hemolytic C1, C3, and C5 titers. C1q and factor B protein levels did not fall. Partial C3 cleavage was also demonstrated in postfilter samples by electrophoretic methods. At 5 min or later, reductions in CH50 titers were much less marked, though significant. Maximal granulocytopenia in the donors was observed within minutes after reinfusion of the first postfilter blood. Circulating granulocytes increased to baseline or higher levels after 10-30 min, while reinfusion of postfilter blood (exhibiting only mild reductions in CH50 titer) continued. In a sixth donor, after the initial FL-associated granulocytopenia had cleared, a fresh set of filters was inserted in the line, and the sequence of C component reduction and granulocytopenia was repeated. The pattern of the observed C component changes was consistent with the activation of the classical C pathway, and possibly also the alternative C pathway, immediately after initial contact of blood with the nylon filters. The temporal association of these C changes with the development of the granulocytopenia in vivo within minutes after reentry of this postfilter blood into the donors’ circulation suggests a causal relationship.